Ultracapacitors are devices that their behaviour are suitable modelled using fractional(non-integer)-order models, thus for their control the fractional-order control methodology is needed. In this paper, non-integer order control is applied to improve the performance of a buck-boost dc-dc power converter with ultracapacitor-based on state feedback techniques. The approach is based on stabilization in the Lyapunov's sense for linear rational order systems.